Mass transfer occurs when advection and diffusion cause the net movement of mass from one location to another location. In chemical engineering and a diversity of industries, mass transfer is an energy-intensive process requiring extensive capital investment. Mass transfer processes and/or systems include, for example, filtration processes and filters, inertial microfluidics, liquid/liquid and gas/liquid separation, bioreactors and chemical reactors, static mixing, feed delivery, adsorption by activated carbon beds, and dispensing systems. The high pressures needed to transport mass and the drag opposing that transport result in substantial energy expenditure.
The filtering of particles from a fluid generally involves moving the particle-filled fluid to impact a filter membrane perpendicularly (known as dead-end filtration) or moving the particle-filled fluid tangentially across a filter membrane (known as cross-flow filtration). Over time, the filter membrane clogs with particles for both of these filtering approaches, increasing the transmembrane pressure and the energy required for filtration. Clogging in dead-end filtering occurs as the particle-filled fluid is pushed against the filter membrane and the extracted particles remain on one side thereof. Clogging in cross-flow filtration also occurs via a phenomenon termed “concentration polarization” whereby small particles accumulate in a layer near the filter membrane surface. In either case, the filter membrane must then be backwashed or mechanically cleaned, chemically treated, or replaced. Each of these options can be time-consuming and/or costly.